Elastic projectile propulsion systems and methods

ABSTRACT

An elastic projectile propulsion system deploys a plurality of springs that bias a common launching cord via a plurality of block and tackle pulleys. Each sheave of the pulley is coupled to the moveable end of a spring such that the force of each spring contributes to the energy imparted to a projectile by the launching cord without adding significant friction or inertial resistance.

CROSS-REFERENCE

This application claims the benefit of U.S. Provisional Application No. 61/867,383, entitled ELASTIC PROJECTILE PROPULSION SYSTEM, filed on Aug. 19, 2013, and 61/946,736, entitled ELASTIC PROJECTIVE PROPULSION SYSTEM, filed Mar. 1, 2014, which applications are incorporated herein by reference.

BACKGROUND

The present disclosure relates to a compact propulsion systems that deploys stored elastic energy to propel a projectile, and more particularly to a compact propulsion system for launching an arrow and other flying projectiles.

Prior methods of launching arrows and other projectiles have deployed elastic energy stored in springs, such as leaf springs in a bow, torsion springs and coil springs, rubber tubes and bands, as well as the elastic energy stored in a stretched launching cord. Various combinations of these elements are known, some of which include a series of pulleys to extend and direct the launching cord in a generally serpentine path. See, for example, U.S. Pat. No. 2,515,205 A to Fieux for Catapult Device for Launching Aerial Machines, issued Jul. 18, 1950.

However, the prior systems have limitations. While metal springs are more reliable over a range of temperatures than rubber springs, the higher mass of the metal springs imposes a velocity limitation.

Bow systems are not compact (typically having a width of at least 12 inches (30.48 centimeters) or more at a widest point), and require large loading force (crossbows typically having 125-200 lbs (56.7-90.72 kilograms) of draw weight), which is overcome by adding heavy, bulky and complicated levers and ratchets, thereby increasing size and weight of the device.

Additionally, bow systems are limited in the ability to reabsorb stored energy without sustaining damage to the bow during launch. Hence, bow systems require a minimum arrow weight be matched proportionately to a draw force of a bow in order to dissipate energy away from the bow during launch and ensure functionality without incurring damage to the bow system. Widely adopted industry standards recommend that a bow never be deployed to launch without an arrow (“dry fired”) and have set a minimum ratio of arrow weight to draw force which, in turn, imposes a velocity limitation.

The devices disclosed herein provide a propulsion configuration that can overcome the above limitations.

SUMMARY

An aspect of the disclosure provides a propulsion device comprising a rigid elongated barrel member having a forward (distal) launching end and an opposing (proximal) stock connecting end, a pair of forward (distal) spring members each mounted to connect at a distal end thereof on opposing sides of the barrel adjacent the forward (distal) launching end, each forward (distal) spring having a distal end connected to the barrel opposite the moveable proximal end, a pair of rear (proximal) spring members, each mounted to connect to the barrel at a proximal end thereof on opposite sides of the barrel adjacent the proximal stock end, a pair of moveable fore pulley blocks, each coupled to the proximal moveable end of each forward spring member and at least one proximal moveable pulley block, connected to the distal moveable end of each rear spring member, a launching cord having each of the opposing ends and engaging both the distal and proximal moveable pulley blocks on opposing sides of the barrel to provide a pair of moveable, counter acting block and tackle pulleys to couple the elastic energy stored in the distal and proximal spring members when a launch cord center is drawn in a proximal direction toward the stock connecting end of the barrel. Components made from elastic materials are resilient and enable the component to spring back into a predetermined shape after a deforming force is removed.

A second aspect of the disclosure provides a method of propelling a projectile, such as an arrow. The method comprises the steps of providing a propulsion device, providing a projectile having a forward (distal) end and a rear (proximal) end opposite the forward end, resting the projectile on a barrel to engage a center of a launching cord at the rear (proximal) end of the projectile, drawing the center of the cord and attached projectile in the rearward (proximal) direction to tension the launching cords engaged in the adjacent moveable pulley blocks attached to the distal and proximal spring members on both opposing sides of the barrel and in turn extend each of the distal and proximal spring members toward the other, releasing the launching cord and projectile to provide a mutual and simultaneous transfer of energy from the tensioned springs and launching cord to the projectile. Alternatively, the linear projectile, such as an arrow, may be secured within the device after the launch cord has been fully tensioned, and thereafter, the user releases the draw on the projectile (e.g., by pulling the trigger, releasing the launch cord, etc.), which causes a transfer of energy from the tensioned springs and launch cord to the projectile.

An aspect of the disclosure is directed to propulsion devices. Suitable propulsion devices, comprise: a) an elongated barrel member forming a cavity having an elongated barrel member proximal end and an elongated barrel member distal end, where the elongated barrel member proximal end engages a mounting stock, b) a pair of forward spring members each having a forward spring member proximal end and a forward spring member distal end, the pair of forward spring members positioned within the cavity of the elongated barrel member wherein the distal ends of the forward spring members connect to a corresponding moveable brace and the proximal ends of the forward spring members connect to a moveable pulley blocks, c) a pair of rearward spring members, each having a rearward spring member proximal end and a rearward spring member distal end, the pair of rearward spring members positioned within the cavity of the elongated barrel member wherein the distal end of the rearward spring members connects to the moveable pulley blocks and the proximal ends of the rearward spring members connects to the corresponding moveable braces, d) at least one pair of forward pulleys, each forward pulley coupled to the forward spring member proximal ends and at least one rearward pulley, connected to each of the rearward spring member distal ends, and e) a launching cord having a first end and a second end which can attach at either the forward moveable pulley blocks or the rearward moveable pulley blocks and traverse a serpentine path around pulleys to engage both the forward pulleys and rearward pulleys. In at least some configurations, the pair of forward pulleys and the rearward pulley are configurable to comprise a counteracting block and tackle pulley which couples an elastic energy stored in the forward spring members and the rearward spring members when the launch cord is drawn rearward toward the stock connecting end of the barrel. Additionally, a rail can be provided and interiorly positioned in the barrel member. The rail can also be configurable to vertically move while remaining stationary horizontally. Additionally, a cocking mechanism and/or trigger assembly can be provided. Propulsion devices are configurable such that they have a width of 12 inches or less. In some configurations, the launching cord is wrapped three or more times around the distal pulley. Additionally, the forward spring members and the rearward spring members are combined in parallel banks, wherein each bank engages one or more moveably pulley blocks.

Another aspect of the disclosure is directed to linear archery systems. The linear archery systems comprise: a) an elongated barrel member forming a cavity having an elongated barrel member proximal end and an elongated barrel member distal end, where the elongated barrel member proximal end engages a mounting stock, b) one or more of a forward spring member each of the one or more forward spring members having a forward spring member proximal end and a forward spring member distal end, the one or more forward spring members positioned within the cavity of the elongated barrel member wherein the distal end of the one or more forward spring members connects to a moveable brace and the proximal ends of the forward spring members connect to a moveable pulley block, c) one or more rearward spring members, each of the one or more rearward spring members having a rearward spring member proximal end and a rearward spring member distal end, the one or more rearward spring members positioned within the cavity of the elongated barrel member wherein the distal end of the one or more rearward spring members connects to the moveable pulley blocks and the proximal ends of the rearward spring members connects to the corresponding moveable brace, d) one or more forward pulleys, each of the one or more forward pulleys coupled to at least one of the one or more forward spring member proximal ends and at least one rearward pulley, connected to the rearward spring member distal end, and e) a launching cord having a first end and a second end which can attach at either the forward moveable pulley blocks or the rearward moveable pulley blocks and traverse a serpentine path around pulleys to engage both the forward pulleys and rearward pulleys. In at least some configurations, the pair of forward pulleys and the rearward pulley are configurable to comprise a counteracting block and tackle pulley which couples an elastic energy stored in the forward spring members and the rearward spring members when the launch cord is drawn rearward toward the stock connecting end of the barrel. Additionally, a rail can be provided that is interiorly positioned in the barrel member. The rail is also configurable to vertically move while remaining stationary horizontally. Additionally, a cocking mechanism and/or trigger assembly can be provided. Configurations of the systems have a width of 12 inches or less. Additionally, the launching cord is wrapped three or more times around the distal pulley.

Still another aspect of the disclosure is directed to self-arresting propulsion systems. The self-arresting propulsion systems comprise: a) an elongated barrel member forming a cavity having an elongated barrel member proximal end and an elongated barrel member distal end, where the elongated barrel member proximal end engages a mounting stock, b) a pair of forward spring members each having a forward spring member proximal end and a forward spring member distal end, the pair of forward spring members positioned within the cavity of the elongated barrel member wherein the distal end of the forward spring members connect to a corresponding moveable brace and the proximal ends of the forward spring members connect to a moveable pulley block, c) a pair of rearward spring members, each having a rearward spring member proximal end and a rearward spring member distal end, the pair of rearward spring members positioned within the cavity of the elongated barrel member wherein the distal end of the rearward spring members connect to the moveable pulley block and the proximal end of the rearward spring members connects to the corresponding moveable brace, d) a pair of forward pulleys, each forward pulley coupled to one of the forward spring member proximal ends and at least one rearward pulley, connected to the rear ward spring member distal end, and e) a launching cord having a first end and a second end which can attach at either the forward moveable pulley blocks or the rearward moveable pulley blocks and traverse a serpentine path around pulleys to engage both the forward pulleys and rearward pulleys, wherein the pair of forward pulleys and the rearward pulley comprise a counteracting block and tackle pulley which couples an elastic energy stored in the forward spring members and the rearward spring members when the launch cord is drawn rearward toward the stock connecting end of the barrel. Additionally, a rail interiorly positioned in the barrel member can be provided. The rail can be configurable to vertically move while remaining stationary horizontally. Some configurations will include a cocking mechanism and/or trigger assembly. As with other configurations, the systems have a width of 12 inches or less. The launching cord is wrapped three or more times around the distal pulley.

Yet another aspect of the disclosure is directed to methods of operating a system according to any of the configurations disclosed. The methods comprise the steps of: providing a propulsion device, drawing the launching cord in the rearward direction to tension the launching cord and extend each of the forward spring member and rearward spring members towards each other, and releasing the launching cord to provide a mutual and simultaneous transfer of energy from the tensioned springs and launching cord. Additionally, the method can include providing a linear projectile, and placing the linear projectile in the barrel of the propulsion system to engage the launching cord, wherein the steps of providing the linear projectile and placing the linear projectile in the barrel of the propulsion system is performed after the step of drawing the launching cord.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference, for all purposes and as if repeated in total in the present application. Additional references of interest include U.S. Pat. No. 4,050,438A to Pfotenhauer issued Sep. 27, 1977 for SPRING TYPE PROJECTING DEVICE; U.S. Pat. No. 4,169,456A to Van House issued Oct. 2, 1979 for SHORT LIMB ARCHERY BOW; U.S. Pat. No. 4,411,248A to Kiveson issued Oct. 25, 1983 for CATAPULT CONSTRUCTION; U.S. Pat. No. 4,703,744A to Taylor et al. issued Nov. 3, 1987 for APPARATUS FOR SHOOTING A PROJECTILE; U.S. Pat. No. 5,243,955A to Farless issued Sep. 14, 1993 for MECHANICAL SHOOTING APPARATUS; U.S. Pat. No. 5,673,677A to Wing issued Oct. 7, 1997, for PROJECTILE LAUNCHING APPARATUS; U.S. Pat. No. 7,578,289B2 to Norkus issued Aug. 25, 2009 for COMPOUND ARCHERY BOW WITH EXTENDED INVERTED STROKE; and PCT Publication WO2012/150387A1 to Lamine published Nov. 8, 2012 for SPEARGUN FOR UNDERWATER FISHING.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which:

FIG. 1A is a top plan view of a propulsion system which includes an outer frame, and FIG. 1B is the same view omitting the outer frame, whereas, FIG. 1C is a side elevation view including the outer frame, and FIG. 1D is the same view as FIG. 1C again omitting the outer frame;

FIG. 2 is a perspective view of the launching cord as it is wrapped between the distal and proximal pulleys within their respective moveable pulley blocks but without the distal moveable pulley blocks;

FIG. 3A is side elevation view of the device in a retracted spring position, whereas FIG. 3B is a side elevation view in an extended spring position or projectile launch ready state; FIG. 3C is a close-up side view of the sliding trigger assembly including the outer frame; FIG. 3D is a close-up front cross-sectional view of the sliding trigger assembly including the outer frame;

FIG. 4 is perspective partial view of the springs in the extended position or projectile launch ready state;

FIG. 5 is a more detailed perspective view of the moveable pulley mechanism attached to the springs in the extended position or projectile launch ready state;

FIG. 6 is a partial enlarged perspective view of FIG. 4 and FIG. 5 that includes the nock of arrow projectile, adjacent the distal moveable pulleys attached to the springs in the retracted position;

FIG. 7A is an top plan view of the outer frame as it connects to the fixed braces, shown in the extended spring position or projectile launch ready state, whereas

FIG. 7B depicts the top plan view with the outer frame omitted to better depict the fixed and moveable brace connections to the springs in the extended position, and

FIG. 7C illustrates the top plan view with the outer frame omitted to better depict the fixed and moveable brace connections with springs in a position during retraction, and

FIG. 7D illustrates the top plan view with the outer frame omitted to better depict the springs in the retracted position;

FIGS. 8A-C are schematic diagrams of the cord, pulley blocks, pulleys and springs representing alternative configurations tested in comparative examples;

FIGS. 9A-H are isolated views of rail mechanisms, such as shown in FIGS. 1 and 7;

FIGS. 10A-C are front and isometric views that depict the positions of the grip as configured in an integrated cocking mechanism;

FIGS. 11A-F are partial side and top views of the passive safety mechanism;

FIGS. 12A-H are partial side and top views detailing the anti-dry-fire mechanism;

FIGS. 13A-D are side and isometric views illustrating the auto-retractable foot claw mechanism;

FIGS. 14 A-C illustrate the adjustable stock; wherein FIGS. 14A-B are partial side views detailing the full range adjustability, and FIG. 14C is a detailed proximal view of the components of the stock release mechanism;

FIGS. 15A-B are isometric, close-up, views of launch cord tensioning terminals; and

FIGS. 16A-B are top views of an arrow retaining system with springs extended and arrow loaded, and springs retracted arrow unloaded.

DETAILED DESCRIPTION

Referring to FIGS. 1 through 16, wherein like reference numerals refer to like components in the various views, there is illustrated therein a new and improved device for an elastic projectile propulsion system, generally denominated 100 herein. The elastic projectile propulsion system is a linear archery system. The elastic projectile propulsion system 100 can be described as a launching device or launcher. Spatial orientation references ‘proximal’ and ‘distal’ have been labeled in the figures as “P” and “D”, respectively, where proximal is situated nearest the user and distal is situated furthest from the user. The systems and devices position the launch cord between moveable pulleys.

The various described embodiments described herein provide multiple benefits, which include for example, stable elastic metal or composite springs which are deployable with a reduced inertial burden imposed by the spring mass on the velocity of the projectile such as an arrow, as the elastic projectile propulsion system 100 couples the force and travel distance of multiple springs utilizing moveable pulleys and an attached launch cord to simultaneously accelerate the launch cord and attached projectile at a velocity that exceeds the velocity of each individual spring moving simultaneously within the system. In addition, the elastic projectile propulsion system 100, which is a launching device, can be very narrow (e.g. 12 inches (30.48 centimeters) or less in width), light-weight (e.g., 9 pounds (4.08 kg) or less in weight), compact (e.g., having a volume of 500 cubic inches (8,193 cubic centimeters), or less). As an example of this benefit, in the comparison to competitive shooting crossbows, a high velocity arrow flight is achieved without a bulky, wide and heavy bow limbs. As well, the stable metal or composite springs within the elastic propulsion system 100 provide more reliable elastic performance under a range of temperate weather conditions compared to propulsion devices utilizing rubber elasticity, which is known to have elastic performance that varies with a wide range of temperate weather conditions.

Additionally, the embodiments described provide for a self-arresting propulsion system which allows the safe use of lighter weight arrows than usable in currently available bows and crossbows, which generally follow industry guidelines that limit arrow weight to 5 grains of arrow weight per pound of bow draw force. As will be appreciated by those skilled in the art, lighter arrows can attain much higher velocities than heavier arrows when launched at the same draw length and force (e.g., power stroke). The propulsion system 100 is capable of safely launching projectiles such as arrows that are less than 5 grains of arrow weight per pound of draw force. Still another advantage to the configurations provided herein is that there is very low draw weight, which is less than 125 lbs. This enables the user to directly cock the device and does not require a cocking device employing significant mechanical advantage. As will be appreciated by those skilled in the art, most crossbows range from 125-200 lbs (56.7-90.72 kilograms) of draw weight and require a cocking assist either as a separate device or as an integrated component in order to gain a mechanical advantage.

Devices and Systems

Turning now to FIG. 1A, a top plan view of an elastic projectile propulsion system 100 is illustrated which includes an elongated outer frame 111, where the length is greater than the width. FIG. 1B is the same view of an elastic projectile propulsion system 100 omitting the outer frame. FIG. 1C is a side elevation view of the elastic projectile propulsion system 100 including the elongated outer frame 111. FIG. 1D is the side elevation of the elastic projectile propulsion system 100 omitting the outer frame. In accordance with the present disclosure, the elastic projectile propulsion system 100 has an elongated outer frame 111 having a cavity therein with an interior surface and an exterior surface, an elongated center rail member 110 having a distally positioned forward launching end 110 a and a proximally positioned opposing stock connecting end 110 b. Elongated center rail member 110 is configurable to connect to a portion of the interior surface of the elongated outer frame 111, along a length of a bottom of the inner wall of the elongated outer frame 111. The connection between the elongated outer frame 111 and the elongated center rail member 110 can be in a stationary position, as illustrated in FIG. 1A and FIG. 1C. One or more fixed braces 220, 230 can be provided to connect to the elongated outer frame 111 on the interior surface and perpendicular to the inner walls of elongated outer frame 111, each of the fixed braces 220, 230 are positionable at opposing ends of the elongated outer frame 111, e.g. at a proximal position and a distal position in a stationary position, as illustrated in FIGS. 1A-D.

Elongated center rail member 110 and fixed braces 220, 230 can be formed integrally with elongated outer frame 111 in a fixed position to form a rigid and robust barrel structure or housing. A pair of forward spring members 120, 120′ positioned distally, are mountable to connect to a fixed brace 220 via moveable braces 127 a, 127′a at a distal spring end 120 a, 120′a thereof on opposing sides of the elongated center rail member 110 adjacent a distally positioned forward launching end 110 a, each of the forward spring members 120, 120′ having a proximal spring ends 120 b, 120′b opposite the distal spring ends 120 a, 120′a. Likewise, a pair of rear spring members 130, 130′ positioned proximally, are mountable to connect to fixed brace 230 via moveable brace 137 a, 137′a at proximal spring ends 130 a, 130′a thereof on opposite sides of the elongated center rail member 110 adjacent the proximally positioned opposing mounting stock 160 connecting end 110 b, with distal spring ends 130 b, 130′b opposite the proximal spring ends 130 a, 130′a. Each of the forward spring members 120, 120′ and the rear spring members 130, 130′ is connectable to a member of a moveable pulley block or block and tackle system 140 (shown in more detail in FIG. 2, FIG. 5, FIG. 6 and FIGS. 15A-B) that deploys the proximal moveable pulley blocks 135, 135′ and distal moveable pulley blocks 125, 125′, and that includes a launch cord 150. It should be noted that distal moveable pulley blocks 125, 125′ are comprised of top moveable pulley block linkages 125 a, 125′a and the lower linkage portion of moveable brackets 127 b, 127′b and are connected to hold the pulley wheels 126 a, 126 b, 126′a, 126′b via pulley wheel axels 129, 129′, as illustrated in FIG. 6. In addition, moveable pulley blocks 135, 135′ are comprised of top moveable pulley block linkage 135 a, 135′a and bottom moveable pulley block linkages 135 b, 135′b and are connected to hold the pulley wheels via pulley wheel axels 139, 139′ as illustrated in FIG. 15A-B.

For a handheld device, as shown in FIG. 1D, it is also preferable to deploy a hand grip 161 or support or mounting stock 160 at the proximal end of the elongated center rail member 110. While the device may be configured to extend and release the launch cord 150 directly by hand, a launch cord release latch 170 can also be used which is activated by trigger 180 which is connected to elongated center rail /10 via trigger assembly 185. Further, the diameter of the distal moveable pulley blocks 125, 125′, and the proximal moveable pulley blocks 135, 135′ is no wider that the forward spring members 120, 120′ and rear spring members 130, 130′ to keep the elastic projectile propulsion system 100 compact (e.g., having a diameter from ¼ inch to ¾ inch). Pulleys or sheaves, which are a grooved wheel as part of a pulley block can include bearings, not shown, to reduce friction, or be provided without bearings.

FIG. 2 is a perspective view of the launch cord 150 as it is wrapped between the distal pulleys and the proximal pulleys within their respective moveable pulley blocks (without illustrating the distal moveable pulley blocks). As illustrated at least one proximal pulley 136, 136′ is connected or coupled via proximal moveable pulley blocks 135, 135′ to a distal spring end of each rear spring members via moveable braces 137 b, 137′b and at least one distal pulley 126 a, 126 b and 126′a, 126′b is coupled or connected to the proximal spring end via distal moveable pulley blocks of each of the forward spring members (distally positioned). A launch cord 150 has a launch cord first end 150 a and a launch cord second end 150 b (opposing launch cord ends) engaging both the proximal moveable pulleys 136, 136′ within blocks 135, 135′ and the distal pulleys 126 a, 126 b and 126′a, 126′b within their respective moveable pulley blocks (not pictured) and on opposing ends of the tackle system to provide a pair of counter acting block and tackle pulleys to couple the elastic energy stored in the forward spring members and rear spring members, when a launch cord center 150 c is drawn rearward (proximal).

Coupling each moveable pulley block and an associated pulley(s) to move with a spring overcomes an inertial burden of metal springs by adding a force of multiple cooperating springs without excess friction. Moreover, it is preferable to provide three wraps of a launch cord 150 between distal pulleys 126 a, 126 b, and proximal pulley 136 and three wraps of launch cord 150 between proximal pulley 126′a, 126′b and proximal pulley 136′, as illustrated in FIG. 2 (which omits the springs that are attached to each moveable pulley block). The springs and pulleys of this configuration arc also shown schematically in FIG. 8C.

The combination of multiple launch cord wraps between pulleys that move in cooperation with the springs on release of the launch cord and the projectile enables a large launch velocity by simultaneously improving the speed at which the force of the launch stroke is transferred to the projectile and facilitates a compact, light-weight, robust and reliable design. First, it should be understood that the launch velocity will be proportional to the product of the launching force and launch stroke, which is the distance over which the force is applied. Second, it should now be understood that the velocity will also be proportional to the speed at which the launching force can be applied. However, coil springs have not been favored for archery propulsion by those skilled in the art because coil springs have been at a compromise between these factors, as increasing the launch force and or stroke through larger or more powerful springs is limited by proportional increase in spring mass and inertia. Although elastomers or rubber materials provide a high energy to mass density, the materials are not reliable below 40° F. (4.4 degree Celsius). Further, the materials can degrade or crack from repeated use and environmental exposure, and are subject to physical damage from other materials they may contact. Metal and composite coil springs are generally more reliable than elastomers or rubber materials when used in these conditions.

FIG. 3A is side elevation view of the device in a retracted spring position, whereas FIG. 3B is a side elevation view in an extended spring position or projectile launch ready state. FIG. 3C is a close-up side view of the sliding trigger assembly including the outer frame and FIG. 3D is a close-up front cross-sectional view of the sliding trigger assembly including the outer frame. When the projectile 10, such as an arrow, is launched the distal moveable pulley blocks 125, 125′ connected to moveable braces 127 b, 127′b arc pulled in a distal direction via forward spring members 120, 120′ and the proximal moveable pulley blocks 135, 135′ connected to moveable braces 137 b, 137′b are pulled in a proximal direction via rear spring members 130, 130′. Thus, as shown in FIG. 3A in the retracted spring position the distal moveable pulley blocks 125, 125′are separated from the moveable pulley blocks 135, 135′ by a distance, first distance L1, which upon loading or extending as shown in FIG. 3B, decreases from the first distance L1 to a lesser distance, second distance L2. The launch strokes is (L1−L2)x where x is a number of launch cords traverses or wraps between opposing the distal moveable pulley blocks 125, 125′ and proximal moveable pulley blocks 135, 135′, which includes the addition of the launch cord center 150 c when in the loading or extending position as shown in FIG. 3B. In this example, L1-L2=7.5 inches and is multiplied by 4 (3 pulley wraps plus the addition of 1 to account for the leverage of the center cord 150 c) and thus produces a launch stroke of 30 inches.

Multiple parallel springs can be employed to engage each distal moveable pulley blocks 125, 125′ or proximal moveable pulley blocks 135, 135′, as shown in FIGS. 3A-3B via a connection to moveable braces 127 b, 127′b and 137 b, 137′b, respectively.

As illustrated in FIGS. 3A-D, the launch cord release latch 170 and hand grip 161 can be attached to a moveable trigger assembly 185 that can travel along the length of the elongated center rail 110. As shown in FIG. 3C and 3D, at the top corners of trigger assembly 185 are roller mounts 186 a, 186′b and 187 a, 187′b (186 a not show in these partial figures) that extend up through slits that run the length of the bottom of the elongated outer frame 111. Launch cord release latch 170, 170′ extend through the same two slits running the length of elongated outer frame 111 on either side of elongated center rail 110. Attached to the ends of roller mounts 186 a, 186′b and 187 a, 187′b are rollers 186, 186′ and 187, 187′(186 not show in these partial figures) that travel within the channel guide shape on either side of the elongated center rail 110. This configuration allows the launch cord release latch 170, hand grip 161 and trigger assembly to travel the length of elongated center rail 110 in both a proximal and distal direction while staying permanently attached to elongated center rail 110. This mechanism provides a method of drawing and releasing the launch cord 150 via the grip 161 for either cocking or uncocking the device. As shown in FIG. 3A-3C, the trigger assembly 185 is permanently attached to a latch hook 181 that can connect and disconnect from the stationary latch pin 162 that is permanently attach to the mounting stock 160.

FIG. 4 is perspective partial view of the springs in the extended position or projectile launch ready state. FIG. 5 is a more detailed perspective view of the moveable pulley mechanism attached to the springs in the extended position or projectile launch ready state. FIG. 6 is a partial enlarged perspective view of FIG. 4 and FIG. 5 that includes the nock of arrow projectile 10, adjacent the distal moveable pulleys attached to the springs in the retracted position. The launch or power stroke can be increased by multiple wraps between the pulleys in the distal moveable pulley blocks 125, 135 associated with opposing springs. However, as the springs move simultaneously upon the release of the launching cord, back to the rest or equilibrium position, while an inertial limitation still exists, the contribution of each spring to the launch velocity is additive, which combined with a large power stroke rated by multiple pulley wraps can overcome these inertial spring barriers and greatly increase the launch velocity of a projectile such as an arrow 10. Further, additional springs can be added in a parallel configuration to each of the moveable braces connected to the moveable pulley blocks, as shown in the second embodiment of FIGS. 3-6, to provide additional force, without significant increase in physical dimensions, other than the minor height increase transverse to the elongated center rail member 110.

As shown in FIG. 5, it also preferable that the moveable braces 127 b, 127′b that connect to the proximal ends of forward spring members 120, 120′ are connected by bridge 225, that extend over and traverse the elongated center rail member 110. Bridge 225 also extends over any projectile such as an arrow 10.

As shown in FIG. 6, the launch cord center 150 c is removably attachable to a nock 300 of projectile such as an arrow 10 and projectiles for release at the time of flight. The nock 300 is a notch in the rearmost end of the arrow which serves to keep the arrow in place on the string, or launch cord 150, as the bow is drawn. However, in the case of complicated projectiles the launch cord 150 may be coupled to the projectile through a more elaborate intermediate assembly (not shown) that runs with the elongated center rail 110, and the projectile launches from the intermediate assembly. Hence, the elongated center rail 110 can be deployed to guide the projectile. In the case of arrow projectiles, the track can be configured minimally, but particularly not to interfere with the flight of the arrow wings. In the case of other projectiles, the elongated center rail 110 can be more substantial, and need not be linear.

As discussed with respect to FIGS. 3-6, forward spring members 120, 120′ and rear spring members 130, 130′ may be combined in a parallel bank, each bank engaging one or more moveable pulley blocks, but preferably four metal or composite coil springs in each forward spring members 120, 120′and three metal or composite coil springs are deployed in each rear spring member 130, 130′. The spring tension within the forward spring members and rear spring members should be balanced with the mechanical advantage of the associated pulleys so that the forward spring members and rear spring members retract simultaneously throughout launch. When using uniform spring dimensions for each spring, determining the balance can be done by matching the number of launch cord 150 connections to each moveable pulley block with the number of springs in each spring member, while the springs are in the extended position. As an example, shown in FIG. 5, in the spring extended position, 3 launch cords connections are made at each of the moveable pulley blocks attached to rear spring members 130, 130, thus each spring member contains 3 springs. Similarly, 4 launch cord 150 connections are made at both moveable pulley blocks attached to forward spring members 120, 120′, thus each spring member contains 4 springs. Alternatively, different spring dimensions in the forward and read spring members can be used to achieve balance with the pulley advantage. The spring members are optionally metal or composite coil springs. Springs are preferably deployed in tension, but a configuration with at least some of the springs in a compression mode is possible.

Further, to the extent some launching devices deploy metal or other torsion springs that work to displace a pulley that directs a launch cord, their performance can likely be improved by adding a second moveable pulley or moveable pulley block connected to a compression or tension spring to wrap the launch cord back to the torsion spring member before it engages the projectile.

FIG. 7A is an top plan view of the outer frame as it connects to the fixed braces, shown in the extended spring position or projectile launch ready state, whereas FIG. 7B depicts the top plan view with the outer frame omitted to better depict the fixed and moveable brace connections to the springs in the extended position, and FIG. 7C illustrates the top plan view with the outer frame omitted to better depict the fixed and moveable brace connections with springs in a position during retraction, and FIG. 7D illustrates the top plan view with the outer frame omitted to better depict the springs in the retracted position.

Additionally, moveable braces 127 a, 127′a and moveable brace 137 a, 137′a can be used to allow free travel through fixed braces 220, 230, respectively, which are firmly attached to the inner walls at opposing ends of elongated outer frame 111 and elongated center rail 110. One or more bumpers 128, 128′, are mounted to the distal ends of moveable braces 127 a, 127′a located on the distal face of fixed brace 220, and bumpers 138, 138′ mounted to proximal ends of moveable brace 137 a, 137′a located on the proximal face of fixed brace 230, as illustrated in FIGS. 7A-D. In the extended position, forward spring members 120, 120′ forces draw the moveable braces 127 a, 127′a in a proximal direction, thus pulling the one or more bumpers 128, 128′ firmly against the distal face of fixed brace 220 which is attached to elongated outer frame 111, and simultaneous the rear spring members 130, 130′ forces draw the moveable brace 137 a, 137′a in a distal direction, thus pulling the bumpers 138, 138′ firmly against the proximal face of fixed brace 230 which is attached to elongated outer frame 111, as show in FIGS. 7A-B. During the process of retracting, forces in forward spring members 120, 120′ move the moveable braces 127 b, 127′b in the distal direction until a stopping point at which the launch cord center 150 c is held stationary, in turn, disengaging the nock 300 as projectile such as an arrow 10 continues to travel in a distal launch direction. Simultaneously, forces in rear spring members 130, 130′ move the moveable brace 137 b, 137′b in a proximal direction until a stopping point at which launch cord 150 is held stationary. Forces not imparted to the projectile 10, continue to travel through forward spring members 120, 120′ and rear spring members 130, 130′. Forward spring members 120, 120′ continue moving in the distal direction and, in turn, push the moveable braces 127 a, 127′a though fixed brace 220, thus moving the bumpers 128, 128′ in a distal direction away from fixed brace 220 (attached to distal end of the elongated outer frame 111), and simultaneously to rear spring members 130, 130′ continue moving in the proximal direction and, in turn, push the moveable brace 137 a, 137′a through fixed brace 230, thus moving the bumpers 138, 138′ in a proximal direction away from fixed brace 230 (attached to the proximal end of the elongated outer frame 111). One or more bumpers 128, 128′ and moveable braces 127 a, 127′a continue moving in a distal direction until counter-acting forces within forward spring members 120, 120′ reach equilibrium and arrest their distal travel progress, thus moving them back in a proximal direction and returning one or more bumpers 128, 128′ to their initial position, flush against the distal face of fixed brace 220, and simultaneously the bumpers 138, 138′ and moveable brace 137 a, 137′a continue moving in a proximal direction until counter-acting forces within rear spring members 130, 130′ reach equilibrium and arrest their proximal travel progress thus moving them back in a distal direction and returning the bumpers 138, 138′ to their initial position flush against the proximal face of fixed brace 230, a steady state, in the retracted spring position, as illustrated in FIG. 7C and FIG. 7D. Hence, these configurations allow excess forces not imparted to the projectile such as an arrow 10 to be reabsorbed and resolved within the system without sustaining damage to the system.

FIGS. 8A-C are schematic diagrams of the cord, pulley blocks, pulleys and springs representing alternative configurations tested in comparative examples with the illustrations showing only the pulley blocks on one side of the center rail, including the associated symmetric half of the launching cord. Further, pulleys that rotate about a common axis or axle of a single pulley block are shown in FIGS. 8A-C as vertically spaced apart to better illustrate the launching cord path and a launch cord first end 150 a forming a terminal connection of half the launch cord 150. Projectile such as an arrow 10 points in the direction it is launched by forward spring members 120 and rear spring members 130. FIG. 8C corresponds to an embodiment of FIG. 1 and FIG. 2. It should be noted that the configurations in FIG. 8A and FIG. 8B both deploy two pulley blocks 125, 135 and in each of two pulley wheels 126 a, 126 b and 136 a, 136 b, respectively, so that the launch cord makes four wraps between the pulleys. In FIG. 8A, however, only the proximal pulley block 135 is moveable as attached to the springs, as the forward or distal pulley blocks 125 has been attached in a fixed point of the distal end of elongated center rail 110. FIG. 8C is as shown in FIGS. 1A-B, with only three pulley wheels utilized in the two moveable pulley blocks. Two pulley wheels 126 a, 126 b were placed in a distal moveable pulley blocks 125 attach to the proximal ends of the forward spring members 120 and one pulley wheel 136 in the moveable pulley block 135 attached to the proximal spring (at the distal spring end), and the string or launch cord 150 ends terminated directly to the proximal springs 130. The bow string or launch cord 150 now traveled around three pulley wheels on either side of the center rail.

Comparative test results revealed that the configuration illustrated in FIG. 8C generated superior arrow velocity and the results are discussed in more detail in the TESTING section below. However, a summary of the results concluded that associating each moveable pulley blocks 125, 135 to move individually with a tensioned spring members, forward spring members 120, and rear spring members 130, respectively, or elastic member in the opposing direction of the opposing pulleys in the block and tackle configuration provided a higher launch velocity than if one set of pulleys was not moveable or was fixed to the stationary part of the embodiment, or the end of the launching cord was attached to a fixed position with respect to the elongated center rail member 110. As each wrap of the launch cord 150 around a pulley 126, 136 introduces friction, it is desirable to minimize the pulley wraps of the launch cord 150, while still obtaining the additive release power and stroke distance of opposing springs: forward spring members 120, and rear spring members 130.

FIGS. 9A-H are isolated views of rail mechanisms, such as shown in FIGS. 1 and 7. FIG. 9A-C are depicted with a large diameter projectile such as an arrow 10, and FIG. 9D-E are depicted with a smaller diameter projectile such as an arrow 10. As illustrated in FIGS. 9A-H, the elongated center rail 110 can be configured with the addition of an over-molded center rail 112 to raise or lower arrows of varying diameters in order to keep the projectile such as an arrow 10 and arrow nock 300 in alignment with launch cord center 150 c. An over-molded center rail 112 is nested on top of the elongated center rail 110 and configured such that the over-molded center rail 112 can raise and lower while remaining in parallel alignment with elongated center rail 110 in order to accommodate arrows of varying diameters. On adjacent sides of the over-molded center rail 112, angled notches have been positioned at the proximal 112 b, center and distal 112 a areas of over-molded center rail 112. Each of the notches 112 c, 112′c, 112 d, 112′d and 112 e, 112′e of over-molded center rail 112 rest upon pins 113 that are mountable into and along adjacent sides of over-molded center rail 112. Notches 112 c, 112′c rest upon pins 113 a, 113′a, notches 112 d, 112′d rest upon pins 113, 113′ and notches 112 e, 112′e rest upon pins 113 b, 113′b. FIG. 9F-H are a close up view of the mechanism used to adjust the over-molded center rail 112. At the proximal end of the over-molded center rail 112, an adjustment screw 114 is mounted to the over-molded center rail 112 through grommet 116. The distal end of adjustment screw 114 connects to clevis end 117. A slotted linkage 119 then connects over-molded center rail 112 to the clevis end 117 such that the slotted end of the linkage is captured within the clevis end 117 via a clevis pin 118. When the adjustment screw 114 is rotated clockwise it draws the over-molded center rail 112 in the proximal and upward direction, as the angled notches in over-molded center rail 112 travel over the pins 113 mountable in the sides of over-molded center rail 112, as shown in FIG. 9H.

FIGS. 10A-C are front and isometric views that depict the positions of the hand grip as configured in an integrated cocking mechanism. Additionally, the hand grip 161 may be configured in two moveable pieces, moveable hand grips 161, 161′ attached to trigger assembly 185 with two hinges 183, 183′, as depicted in FIG. 10A-C, to aid in the cocking or uncocking the device. A scope mount 201 may also be attached to elongated outer frame 111 to mount a scope 200.

FIGS. 11A-F are partial side and top views of the passive safety mechanism. Additionally, the mechanisms within the trigger assembly 185 can be configured to passively activate a safety mechanism (which prohibits the deployment of the propulsion system) during the cocking process, as depicted in FIGS. 11A-F. In order for trigger 180 to release the launch cord release latch 770, 170′ (and deploy the propulsion system), trigger 180 must rotate around its axis pin 182, which rotates the top of trigger 180 in a distal direction away from contact with pin 175 that is connected to the launch cord release latch 170, 170′. When safety pin 174 is moved into the proximal position (SAFE position), beyond ball stud 176 and into the safety pin catch groove in the top of trigger 180, trigger 180 is not able to rotate into a position to allow launch cord release latch 170, 170′ to deploy the propulsion system, as shown in FIG. 11E. Safety pin 174 is mounted to the end of a first toggle arm 173 a which is joined in a perpendicular position to a second toggle arm 173 b in a ridged fashion. Both toggle arms are pivotable on axis pin 172 at the point where the first toggle arm 173 a and second toggle arm 173 b are joined. When the second toggle arm 773 b is moved upward it moves the attached safety pin 174 into a SAFE position via the first toggle arm 173 a. The pin 175 of launch cord release latch 170, 170′ is positioned below the second toggle arm 173 b. Launch cord release latch 170, 170′ is mounted within trigger assembly 185 via axis pin 171 so that launch cord release latch 170, 170′ may tilt backward (proximally) when the top of launch cord release latch 170, 170′ makes contact with the launch cord center 150 c and moves in a distal direction beyond the launch cord center 150 c, during the cocking process. As launch cord release latch 170, 170′ tilts backward its pin 175 moves upward thus moving the second toggle arm 173 b upward, and thus moves safety pin 174 into a SAFE position, as illustrated in FIG. 11C. Safety pin 174 can then be manually moved in a distal direction, out of the SAFE position, in order to allow trigger 180 to be actuated (and deploy the propulsion system).

In another configuration a launch cord release latch 170, 170′ as shown in FIG. 11, is deployable to hold the launch cord 150 with attached projectile, such as an arrow (not shown) and at least one of the springs in the extended position—until released by a trigger 180. The springs can be metal or composite coil springs, preferably tension springs, but can also be elastic materials, such as rubber tubing and the like. Forward spring members 120, 120′ and rear spring members 130, 130′ are mounted parallel to elongated center rail member 110; however, as will be appreciated by those skilled in the art, the forward spring members 120, 120′ and rear spring members 730, 130′ can be mounted in different orientations, with the attached moveable pulley blocks deployed to redirect the launch cord 150 to propel the projectile such as an arrow 10 along the center rail direction without departing from the scope of the disclosure. Further, it should be appreciated that elastic energy is generally stored in the launching cord, as well as the springs. Hence, nothing precludes all or part of the launching cord from being formed of a rubber or elastomer such as a band or tubing, although this might only be desired in isothermal warm environments.

FIGS. 12A-H are partial side and top views detailing the anti-dry-fire mechanism. To further enhance safety, a mechanism can be added to ensure that the propulsion system cannot be deployed without an arrow nocked in the launch cord, as illustrated in FIGS. 12A-H. In the instant configuration, a string catch 164 is mounted via hinge to the top of mounting stock 160. In the absence of a projectile such as an arrow 10 connected by its nock 300 to launch cord center 150 c, string catch 164 is allowed to rest on the launch cord center 150 c in a position that is able to arrest the travel of the launch cord center 150 c from full deployment, as depicted in FIG. 12C. The distal end of string catch 164 is shaped in an angle that is slight proximal and downward to ensure that string catch 164 does not prohibit the cocking process. During the cocking process, the angular shape of the distal end on string catch 164 encourages string catch 164 to pivot upward from its hinge mount, allowing the launch cord center 150 c to move in a proximal direction, past string catch 164, without significant interference. Additionally, as shown in FIG. 12G, a push arm 165 is connected to the underside of string catch 164 via a hinge connection. The push arm 165 extends downward and rests on top of the latch hook 181. During the de-cocking process and in the absence of a projectile such as an arrow 10, when latch hook 181 is lifted upwards, push arm 165 is also pushed upwards, which in turn lifts string catch 164 upwards and thus out of contact with launch cord center 151 c as it travels down a distal path. This mechanism ensures that the string catch 164 is prohibited from interfering with the launch cord center 150 c during de-cocking, even when a projectile such as an arrow 10 is not engaged by its nock 300 to launch cord center 150 c.

The trigger assembly 185 is configured to attach to the mounting stock 160 via a latch hook 181 installed into the trigger assembly 185. The latch hook 181 interfaces with a corresponding stationary latch pin 162 that is located in the lower portion of the mounting stock 160, as shown in FIG. 12C. This mechanism allows the trigger assembly 185 and associated launch cord release latch 170, 170′ to secure the launch cord center 150 c in a fixed position at the proximal end of the elastic projectile propulsion system 100 during the fully cocked or launch-ready state. The latch hook 181 may be disengaged from the corresponding stationary latch pin 162 in mounting stock 160 allowing the trigger assembly 185 to move freely in the distal direction while de-cocking the device, as illustrated in FIG. 12G.

FIGS. 13A-D are side and isometric views illustrating the auto-retractable foot claw mechanism. In another configuration, the elastic projectile propulsion system 100 may include a foot claw 221 to aid in the cocking process, as illustrated in FIGS. 13A-D. In the present execution, the foot claw 221 is attached through the spring wall 220 via two foot claw mounts 222, 222′. On the proximal end of each of the foot claw mounts 222, 222′ coil springs 223, 223′ are attached to keep the foot claw 221 in the retracted position against the elongated outer frame 111. This configuration allows the foot claw to increases accessible foot space during use, and then, when not in use, the foot claw space is minimized to reduce potential interference with other operations of the elastic projectile propulsion system 100.

FIGS. 14 A-C illustrates the adjustable stock; wherein FIGS. 14A-B are partial side views detailing the full range adjustability, and FIG. 14C is a detailed proximal view of the components of the stock release mechanism. As depicted in FIG. 14A-C, an adjustable shoulder stock may be included in the elastic projectile propulsion system 100. A shoulder stock 231 is attached to the proximal ends of two of the stock mounting rods 232, 232′. The distal ends of the stock mount rods 232, 232′ are mounted through holes in mounting stock 160, elliptical holes in each of the release buttons 233, 233′ and holes in the spring wall 230, as to allow the stock mounting rods 232, 232′ to extend in a proximal direction or retract toward mounting stock 160. On the surface of each of the stock mounting rods 232, 232′, running the length of each rod, is a series of banded notches. As illustrated in FIG. 14C, the release buttons 233, 233′ are inset mounted into either side of mounting stock 160, and can pivot on axis bolts 235, 235′ within the inset pattern of mounting stock 160. The release buttons 233, 233′ are maintained in their opposing, extreme positions of travel via two coil springs 234, 234′ such that their outer edges each extend beyond either edge of mounting stock 160. In this position, the inner edge of each elliptical hole within each release buttons 233, 233′ is encouraged into notches on the side of each of the stock mounting rods 232, 232′. In this position the stock mounting rods arc prohibited from extending or retracting. Both release buttons 233, 233′ can be pressed inward at the same time in order to allow each of the stock mounting rods 232, 232′ to be extended or released. This configuration allows the stock to be adjusted to fit users with varying physical needs and allows the stock to be minimized during non-use in order to minimize potential interference with transportation or storage of the elastic projectile propulsion system 100.

FIGS. 15A-B are isometric, close-up, views of launch cord tensioning terminals. It should be understood that the launch cord 150 first end 750 a and second end 150 b can be attached to the proximal ends of the forward spring members, but preferably the distal ends of the rear spring members 130, 130′. In at least some configurations, the launch cord first end 150 a and launch cord second end 150 b are attached to two respective launch cord tensioning mechanisms located below the at least one proximal pulley 136, 136′ and the bottom of the proximal moveable pulley block linkages 135 b, 135′b, which allow the launch cord 150 to be tensioned in fine increments, as depicted in FIG. 15 A-B. The launch cord tensioning mechanism is comprised of cord end spools 151, 157′ and ratchets 152, 152′ which are mounted in fixed positions to pulley wheel axels 739, 739′, such that they rotate when the top of pulley wheel axels 139 or 139′ are turned with a screw driver. Pawls 153, 153′ attach to pulley block linkage pins 134, 134′ and engage ratchets 152, 152′ in a manner that allows cord end spools 151, 151′ to maintain launch cord tension after pulley wheel axels 139, 139′are tightened.

The moveable pulley blocks are attachable to either the distal or proximal spring members that deploy a plurality of pulleys be configured such that each pulley in the block rotate independently of the others.

However, alternatively, each wrap of the launching cord can connect multiple pulleys that are attached to the spring ends, each moveable pulley block having a single pulley.

FIGS. 16A-B are top views of an arrow retaining system with springs extended and arrow loaded, and springs retracted arrow unloaded. Additionally, the elastic projectile propulsion system 100 can be configured to launch arrows of widely varying lengths and arrows that are shorter that the length of the draw or power stroke of the device, as illustrated in FIG. 16A-B. When arrow retaining spring 115, attached within elongated outer frame 111, is located at the mid-point between the launch cord release latch 170, 170′ and distal spring wall 220, the arrow retaining spring 115 maintains contact with the projectile such as an arrow 10 throughout the entire power stroke of launch cord 150. The configuration ensures that arrow point 10 a of projectile such as an arrow 10 will exit the hole in spring wall 220 without making contact with spring wall 220. The result is that shorter, lighter weight arrows may be safely launched arid can attain higher arrow velocity than longer, heavier arrows without any other modifications to the elastic projectile propulsion system 100.

Methods

Methods include operation of the devices disclosed above. In practice, a user obtains a linear projectile, such as an arrow, mounts the projectile in the barrel of the device to engage the launch cord. Once the projectile is secured within the device, the user draws the projectile in a rearward direction to tension the launch cords and extend each of the forward springs and rearward springs. Thereafter, the user releases the draw on the projectile (e.g., by pulling the trigger, releasing the launch cord, etc.), which causes a transfer of energy from the tensioned springs and launch cord to the projectile. Alternatively, the linear projectile, such as an arrow, may be secured within the device after the launch cord has been fully tensioned, and thereafter, the user releases the draw on the projectile (e.g., by pulling the trigger, releasing the launch cord, etc.), which causes a transfer of energy from the tensioned springs and launch cord to the projectile.

Testing

Various configurations of the propulsion mechanism were tested to determine superior arrow velocity, as illustrated in FIG. 8A-8C. In all tests, the power stroke was 30″ for launching a 1 oz. (2.8.35 grams) arrow 33.5 inches (85.09 centimeters) in length, with the arrow flight velocity subsequently measured with a RADARCHRON® brand Doppler radar velocity sensor meter.

As shown in FIG. 8A, the propulsion mechanism was configured so that the front pulleys 126 a, 126 b were held stationary as the distal moveable pulley blocks 125 were attached to a distal, fixed part of the center rail. The forward spring members 120, 120′ and rear spring members 130, 130′ were connected into series attached to the proximal moveable pulley blocks 135. The velocity result of one test was 163 ft/sec (4968 centimeters/second).

The embodiment of FIG. 8B used the same four springs (two springs being positioned on each side of the elongated center rail 110) as in FIG. 8A, however, forward spring members 120 were attached to the distal end of elongated center rail 110 with the distal moveable pulley blocks 125 (containing two pulley wheels) attached to the proximal end of forward spring members 120, 120′. The string ends were terminated directly to the forward springs just under the distal moveable pulley blocks 125. Initial spring tension was the same as the example described with respect to FIG. 8A. The launch cord 150, or bow string, traveled around four pulley wheels in each moveable pulley block. The three flight test results were:

1) 197 ft/sec (6005 centimeters/second),

2) 199 ft/sec (6066 centimeters/second),

3) 196 ft/sec (5974 centimeters/second).

Variances in velocity were likely due to minor adjustments made to the arrow rest between each test.

The propulsion mechanism was also configured as shown in FIG. 8C as shown in FIGS. 1A-B, with only three pulley wheels utilized in the two moveable pulley blocks. Two pulley wheels 126 a, 126 b were placed in a distal moveable pulley blocks 125 attach to the proximal ends of the distally positioned, forward spring members 120 and one pulley wheel 136 in the moveable pulley block 135 attached to the proximal spring (at the distal spring end), and the string or launch cord 150 ends terminated directly to the proximal springs 130. The bow string or launch cord 150 now traveled around three pulley wheels on either side of the center rail. The velocity result of ‘test one’ was 210 ft/sec (6401 centimeters/second). Initial tension in the bow string or launch cord was increased further by visibly removing slack from the launch cord. While initial tension was not measured, it did not appear to separate the extension spring coils. The velocity result of ‘test two’ was 228 ft/sec (6949 centimeters/second). Initial tension was then further increased in the bow string or launch cord 150 so that the initial tension was taken from the spring, separating the coils no more than ⅛″. The velocity result of this test was 246 ft/sec (7498 centimeters/second).

While the highest velocities achieved during tests peaked at 339 ft/sec (1.033e+004 centimeters/second) utilizing a 270 grain arrow at 30 inch (76.2 centimeters) draw length and 78 lbs (35.38 kilograms) draw force, it was discovered that some energy was lost in the launch cord 150 being stretched. It is assumed that solely utilizing a more robust launch cord 150 will result in greater velocities.

As well, it was discovered after velocity testing concluded that utilizing the same spring wire and outer diameter design with a slight increase in spring length resulted in the ability to generate equal or more energy in the power stroke with a significant decrease in draw length. For example, the same spring design used in all the tests was increased in length by 0.9″ and resulted in the ability to decrease the draw length by 6″ while generating a ˜2% increase in power stroke foot-pounds, all with the same 78 lbs (35.38 kilograms) draw force. This was achieved by increasing the initial tension in the springs via tightening of the launch cord which increased the total amount of force that was distributed over the length of the shortened draw stroke. It was also realized that the addition of more pulleys and resulting increase in pulley ratio would allow the use of shorter, more powerful springs to distribute their force over similar or greater draw lengths. It is reasonable to believe that future tests are likely to reveal increases in arrow speeds as shorter, lighter arrows matched to the reduced draw length, with a slight increase in power stroke force will result in more velocity. As well, overall device length can be reduced by a shorter draw length, consistent with a more compact and maneuverable design.

Testing of the shock absorbing system described above was conducted to assess damage caused to the entire system including the elastic projectile propulsion system 100 as a result of launching a projectile such as an arrow 10 not meeting minimum current standards of weight to draw force ratio. The commonly followed industry standard, set and maintained by the International Bowhunting Organization (IBO), is prescribed in a ratio that states an arrow typically weighs at least 5 grains per every one pound of draw force (for bows generating arrow velocities above 290 feet per second (8839 centimeters/second)). Testing was performed with arrows weighing a little as 270 grains (30″ in length) at a draw force of 78 pounds (35.38 kilograms), resulting in a testing ratio of approximately 3.5 grains per one pound of draw force (generating arrow speeds significantly above 290 feet per second (8839 centimeters/second)). Though testing was not conducted to the point of failure, repeated launches did not result in any observed damage to the elastic projectile propulsion system 100. While dry fire tests (without an arrow) were not performed, it is believed that parameters of the described shock absorbing system are capable of being adjusted to achieve dry fire without damage to the elastic projectile propulsion system 100. The demonstrated ability of the propulsion system 100 to reabsorb stored energy not imparted to the arrow upon release and thus launch lighter arrows at equal draw forces compared to conventional bow systems provides an advantage in the ability to increase arrow velocity without increasing draw force or causing corresponding damage to the system.

While preferred embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby. 

What is claimed is:
 1. A propulsion device, comprising: a forward spring member having a forward spring member proximal end and a forward spring member distal end, wherein the distal end of the forward spring member connects to a first brace and the proximal end of the forward spring member connects to a distal moveable pulley block, a rearward spring member having a rearward spring member proximal end and a rearward spring member distal end, wherein the distal end of the rearward spring member connects to a proximal moveable pulley block and the proximal end of the rearward spring member connects to a second brace, at least one forward pulley coupled to the forward spring member proximal end and at least one rearward pulley connected to the rearward spring member distal end, and a launching cord engaging the forward pulley and the rearward pulley.
 2. The propulsion system of claim 1, wherein the at least one forward pulley and the at least one rearward pulley comprise a counteracting block and tackle pulley assembly which couples an elastic energy stored in the forward spring member and the rearward spring member when the launch cord is drawn rearward.
 3. The propulsion device of claim 1, further comprising a rail with a distal fixed brace at a distal end thereof and a proximal fixed brace at a proximal end thereof, the distal fixed brace supporting the first moveable brace and the proximal fixed brace supporting the second moveable brace.
 4. The propulsion device of claim 3, wherein the rail is configurable to vertically move while remaining stationary horizontally.
 5. The propulsion device of claim 1, further comprising a cocking mechanism.
 6. The propulsion device of claim 1, wherein the propulsion device has a width of 12 inches or less.
 7. The propulsion device of claim 1, further comprising a trigger assembly.
 8. The propulsion device of claim 1, wherein the at least one forward pulley comprises a first forward pulley, the device further comprising a second forward pulley.
 9. The propulsion device of claim 1, wherein the forward spring member comprises a first forward spring member and the rearward spring member comprises a first rearward spring member, the device further comprising: a second forward spring member; and a second rearward spring member.
 10. The propulsion device of claim 9, wherein the first and second forward spring members and the first and second rearward spring members are combined in parallel banks, wherein a first one of the parallel banks engages the first moveable pulley block and a second one of the parallel banks engages the second movable pulley block.
 11. A propulsion device for propelling a projectile therefrom, comprising: an elongated member having a proximal fixed base and a distal fixed base; a forward spring member attached at a distal end thereof to the distal fixed base; a distal moveable pulley block attached to a proximal end of the forward spring member; at least a first and second distal pulley spaced apart and disposed on the distal moveable pulley block; a rearward spring member attached at a proximal end thereof to the proximal fixed base; a proximal moveable pulley block attached to a distal end of the rearward spring member; at least one proximal pulley disposed on the proximal moveable pulley block; and a launching cord spanning between the at least one proximal pulley and the first and second distal pulleys.
 12. The propulsion device of claim 11, wherein the launching cord is attached at a first end to the proximal moveable pulley block and extends about the first distal pulley, returns to the at least one proximal pulley, extends back to the first distal pulley, continues to the second distal pulley, extends to the at least one proximal pulley, back to the second distal pulley, and terminates at a second end attached to the proximal moveable pulley block.
 13. The propulsion device of claim 12, wherein at least one of the first end and the second end of the launching cord is attached to an adjustment mechanism to adjust a length of the launching cord.
 14. The propulsion device of claim 11, wherein a launch cord center is disposed between the first and second distal pulleys, wherein the launch cord center is configured to receive a portion of one end of the projectile, wherein the launch cord center is moved proximally to achieve a cocked configuration.
 15. The propulsion device of claim 11, further comprising a passive safety mechanism configured to prevent unintentional discharge of the projectile when the propulsion system is in a cocked configuration.
 16. The propulsion device of claim 11, further comprising: a distal moveable brace interconnecting a distal end of the forward spring with the distal fixed brace, the distal moveable brace permitting movement between the distal end of the forward spring and the distal fixed brace; and a proximal moveable brace interconnecting a proximal end of the rearward spring with the proximal fixed brace, the proximal moveable brace permitting movement between the proximal end of the rearward spring and the proximal fixed brace.
 17. The propulsion device of claim 11, further comprising an adjustable over-molded center rail configured to support the projectile, the adjustable over-molded center rail running along a length of the rail and being adjustable to adjust the position of the projectile relative to the rail.
 18. The propulsion device of claim 11, further comprising a launching cord catch operable to secure the launching cord in a cocked configuration when the projectile is absent, thereby preventing dry-firing of the propulsion system.
 19. The propulsion device of claim 11, further comprising a foot claw resiliently extendable from the distal end of the rail.
 20. A propulsion device, comprising: a rail comprising a proximal fixed base and a distal fixed base; a forward spring member attached at a distal end thereof to the distal fixed base; a distal moveable pulley block attached to a proximal end of the forward spring member; at least a first and second distal pulley spaced apart and disposed on the distal moveable pulley block; at rearward spring member attached at a proximal end thereof to the proximal fixed base; a proximal moveable pulley block attached to a distal end of the rearward spring member; at least one proximal pulley disposed on the proximal moveable pulley block; and a launching cord spanning between the at least one proximal pulley and the first and second distal pulleys, wherein when the launching cord is pulled proximally from a launching cord center region formed between the first and second distal pulleys, a first force is exerted on the distal moveable pulley block by the forward spring member and a second force is exerted on the proximal moveable pulley block by the rearward spring member; and a quantity of the proximal pulleys, a quantity of the distal pulleys, a configuration of the launching cord, and a spring constant of the rearward and forward spring members are chosen to substantially balance the first force and the second force.
 21. The propulsion device of claim 20, wherein the launching cord is attached at the first end to the proximal moveable pulley block and extends about the first distal pulley, returns to the at least one proximal pulley, extends back to the first distal pulley, continues to the second distal pulley, extends to the at least one proximal pulley, back to the second distal pulley, and terminates at the second end attached to the proximal moveable pulley block.
 22. The propulsion device of claim 20, wherein: the forward spring includes at least one set of forward springs, the at least one set including a first forward spring and a second forward spring, the first and second forward springs being disposed on opposite sides of the rail; and the rearward spring includes at least one set of rearward springs, the at least one set including a first rearward spring and a second rearward spring, the first and second rearward springs being disposed on opposite sides of the rail. 